<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>计算器</title>
    <script src="https://unpkg.com/vue"></script>
</head>
<body>
<div id="app">
    <input type="text" v-model="n1">

    <select name="" id="" v-model="opt">
        <option value="+">+</option>
        <option value="-">-</option>
        <option value="*">*</option>
        <option value="/">/</option>
    </select>
    <input type="text" v-model="n2">
    <input type="button" value="=" @click="calc">
    <input type="text" v-model="result">
</div>

</body>
<script>
    var vm = new Vue({
        el: '#app',
        data: {
            n1: 0,
            n2: 0,
            result: 0,
            opt: '+',
            msg: '大家好哈哈哈哈，你们好啊。'
        },
        methods: {
            calc() {
                console.log('我变了');
                switch (this.opt) {
                    case '+':
                        this.result = this.n1 + this.n2;
                        break;
                    case '-':
                        this.result = this.n1 - this.n2;
                        break;
                    case '*':
                        this.result = this.n1 * this.n2;
                        break;
                    case '/':
                        this.result = this.n1 / this.n2;
                        break;

                }
            }
        }

    })
</script>
</html>